606 



Fishery Bulletin 103(4) 



There was a lag period between the time of formation 

 of the first annual growth mark and the actual one- 

 year birthdate. The first annular mark was deposited 

 between 15 and 19 months of age or at 1.25 to 1.6 

 years of age (Wenner and McDonough 3 ). 



Sexual differentiation 



The smallest sexually differentiated male was 137 mm 

 (Fig. 5). Male striped mullet 126 to 150 mm TL were 

 eight to twelve months old (McDonough and Wenner, 

 2003). The first sexually differentiated 

 female was 164 mm TL. Females 151 to 

 175 mm would have been approximately one 

 year old (McDonough and Wenner, 2003). 

 Specimens greater than 200 mm were at 

 least 50% sexually differentiated. Only 

 1.5% of specimens over 300 mm remained 

 undifferentiated. The largest sexually 

 undifferentiated specimen was 325 mm. 

 All fish >325 mm, although still possibly 

 sexually immature, were fully sexually dif- 

 ferentiated. The ratio of males to females 

 was 2:1 until the fish were larger than 325 

 mm <x 2 n=0 05 =2543.9, df=2). The ratio of 

 males to females was 1:3.8 for fish >325 

 mm( / 2 „ =005 =352.8, df=l). 



The sex ratio by age class showed 98.9% 

 of the age-0 specimens were sexually undif- 

 ferentiated (Fig. 6). The few age-0 fish that 

 were differentiated were all males. At first 

 annulus deposition, 91.9% of the specimens 

 had differentiated. There were a few speci- 

 mens (0.8% I that remained undifferenti- 

 ated to 3 years old, but all striped mullet 

 age 4 or older were completely differen- 

 tiated. The sex ratio of males to females 

 in the one-year-old age class was 1.0:0.25 



80 



70 



<d 60 



0= 50 



10 



I 



I 



tototoOtoOtoOtoto.toOtoO.to 



<V to *. O IV v v <y <V „to A 4? <J/ <p A , 



toOtoOtoO.toO 



<V to \ ,o ,<v ,to A ,o 



V V > to to to to <0 



ri7toto*^fo'^to'-.to'^to K ~to*^.to^to''--.<£ 

 ^ ^. V ^ J ^ fv fv (V <V ^ <0 <0 °D > > > > 



- to -- .to 

 o 0/ to 'v 

 to to to to 



Undifferentiated 



Male 



Female 



Size class (mm) 



Figure 5 



Sex by size class (25-mm size classes) for striped mullet iMugil cepha- 

 lus L.) from South Carolina estuaries, October 1997 to December 

 2000. n = 6284. 



<r„= 



- = 1065.4, df=2). At age 2 the ratio 



was 1.0:0.68 (x 2 a= oos =502.6, df=2) and at 

 age 3 the ratio had reversed to 0.32:1.0 

 (^(,05=312.5, df=2). 



Size and age at maturity 



The onset of spermatogenesis in males was 

 first observed at 248 mm (Fig. 7A). The first 

 running, ripe males occurred at 291 mm 

 and this developmental stage was found in 

 all larger sizes. Postspawning males were 

 found only between November and March 

 in mullets larger than 325 mm. Resting 

 mature males were found in every month 

 and occurred in most size classes greater 

 than 251 mm. These resting males made 

 up fewer than 50% of the specimens from 

 any particular size class. A small percent- 



tenner, C. A., and C.J. McDonough. 2001. Co- 

 operative research on the biology and assess- 

 ment of nearshore and estuarine fishes along 

 the southeast coast of the U.S.: Part IV: Striped 

 mullet, Mugil cephalus, p. 17-23. Final Report, 

 Grant no. NA77FF0550. Marine Resources 

 Research Institute, South Carolina Dep. Natu- 

 ral Resources, P.O. Box 12559 Charleston, SC 

 29422-2559. 



